. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. External Characters of Arenicola 33 External Characters.âAll the species of Arenicola are elongate, cylindrical worms, wliich live, when adult, in sand or mud, or in coarse gravel. Some of the species, especially A. marina, lovcni and cristaia, may attain a length of 400 mm. ; one specimen of ^. cristata was as much as 515 mm. long and 75 mm. in girth. Examples of tliis genus have the morphological components found in other Polychaeta, namely, prostomium, peristomium, a number of body-segments, and
. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. External Characters of Arenicola 33 External Characters.âAll the species of Arenicola are elongate, cylindrical worms, wliich live, when adult, in sand or mud, or in coarse gravel. Some of the species, especially A. marina, lovcni and cristaia, may attain a length of 400 mm. ; one specimen of ^. cristata was as much as 515 mm. long and 75 mm. in girth. Examples of tliis genus have the morphological components found in other Polychaeta, namely, prostomium, peristomium, a number of body-segments, and a terminal segment or pygidium, but the last named has generally been lost in the adult. A certain number, or all, of the Ijody-segments (except the first) bear parapodia, but the latter and the prostomium are considerably modified and reduced, as compared with the corresponding structures of more active, mobile Polychaeta, such as Nereis (I'l. XII, Eigs. 3G, 37, 38). In the caudate species of Arenicola the prostomium (Eigs. 1, 2) is a small trilobate structure,^ which, even in large specimens, seldom X2. Per. ;⢠â ' AW Fig. 1.âArenicola loveni. Anterior end, dorsal as- pect. PR. Prostomium ; Per. Peristomium ; Nuchal {troove ; Achaetoug lx)dy-segnient; First chaetiferous Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ashworth, James Hartley, 1874-1936; Ashworth, James Hartley. London, Printed by Order of the Trustees of the British Museum
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